The invention relates to a bearing arrangement for the support of tensile forces, in particular for the suspended mounting of a mass, in order to simulate the weightlessness of the latter in a gravitational field, the bearing arrangement having a first bearing element comprising at least one magnet and a second, metallic bearing element which is attracted magnetically by a first bearing element.
A bearing arrangement of this type is known, for example, from DE 195 01 571 A1.
The invention relates, furthermore, to a bearing head for the bearing arrangement, with a bearing body into which a magnet is integrated.
Satellites are usually equipped, for the supply of power, with foldable solar panels which, during transport from Earth into orbit, are folded together and rest against the outer casing of the satellite. In orbit, after the satellite has been released, these solar panels are then deployed in a zigzag-like manner by means of a deploying mechanism.
This deployment of the solar panels is critical to the system, since the supply of power to the satellite is not ensured without sufficiently and completely unfolded solar panels, and the satellite then cannot be used at all or can be used only to a restricted extent. The deployment operation therefore has to be simulated on Earth and the corresponding mechanism tested.
For this simulation and for this testing operation, the joints of a solar panel arrangement have hitherto been suspended on a rolling bearing track mounted on the ceiling, the corresponding suspension devices being capable of moving about the vertical axis within the rolling bearing track in the longitudinal and transverse directions and at their suspension point. A fundamentally free movement of the unfolding solar panel arrangement was thereby achieved during the deployment operation. However, frictional forces arise in the rolling bearings both in the longitudinal direction and in the transverse direction and also in the rotary bearing of the suspension and do not allow a completely free movement of the unfolding solar panel arrangement, as is the case under conditions of weightlessness in space. Furthermore, the suspension of the solar panels gives rise, in the region of their joints, to a gravity-induced axial force in the joints which in the joints causes frictional resistances which do not occur under conditions of weightlessness. The suspension of the solar panels of this test apparatus, which is generally known and cannot be vouched for by prior art, is therefore suitable only to a limited degree for ensuring an actual free moveability of the deploying solar panels.
It is not only the above-described operation of deploying solar panels which requires a load suspension system capable of being moved without friction. In many other sectors of manufacturing, assembly or conveying technology it is necessary to move suspended loads virtually without friction in a horizontal plane. This is necessary particularly when highly accurate positioning of the load is to be carried out. Such highly accurate positioning is not possible in transport systems where friction occurs, since, because of the friction, there is always an, albeit only slightly detectable, jolt-like movement of the conveying system.
It is therefore an object of the present invention to provide a generic bearing arrangement which, on the one hand, reliably supports tensile forces and, on the other hand, allows virtually frictionless movement in one plane and about a vertical axis.
This object is achieved, according to the invention, in that at least one of the bearing elements has, in its bearing surface, gas outflow nozzles which are loaded by a compressed gas, so that a gas stream flowing out of the gas outflow nozzles forms a gas cushion between the bearing elements attracting one another due to the magnetic force, said gas cushion keeping the bearing elements at a distance from one another. The magnetic attraction force between the bearing elements is, in this case, equal to the sum of the tensile force exerted by the mass and the first bearing element and the repulsion force of the gas cushion.
The combination of magnetic retention and compressed gas bearing makes it possible in a reliable way to build up a holding force between the two bearing elements which reliably supports the tensile forces, without a mechanical connection between the two bearing elements being made at the same time.
U.S. Pat. No. 4,860,600 discloses a microgravity simulator, in which air bearings are used to support a mass to be tested. However, in this known arrangement, the air bearings act counter to gravity so that here a standing arrangement, that is to say a compressive force, is supported by the air bearings. However, where very narrow and high masses to be tested are concerned, as is the case, for example, with solar panels, even the least possible lateral deflections can cause tilting forces which may nullify a conventional standing air mounting according to U.S. Pat. No. 4,860,600 due to tilting moments. A standing gas pressure bearing arrangement having the same disadvantages is also known from U.S. Pat. No. 5,501,114.
It is advantageous, in the bearing arrangement according to the invention, that the suspended arrangement of the mass, and therefore the design of the bearing arrangement as a suspended bearing and not as a standing bearing, is relatively immune to deflections even of a thin high mass, since a stable equilibrium always prevails in a suspended mounting, whereas an unstable equilibrium always prevails in a standing mounting.
In an advantageous development, the first, magnet-equipped bearing element also has the gas outflow nozzles for generating the gas cushion. This bearing arrangement is advantageous in manufacturing terms and from a sales point of view, since only one bearing element has to be of a technologically high-quality design, whereas the other bearing element can be designed relatively simply.
It is also advantageous if the first, magnet-equipped bearing element has a plurality of bearing means, and if the second bearing element is formed by an essentially planar metal plate. The provision of a planar metal plate as the second bearing element makes it possible to concentrate the entire functionality of the bearing arrangement according to the invention onto the first, magnet-equipped bearing element.
Preferably, at the same time, the metal plate forming the second bearing element is arranged fixedly, and the first, magnet-equipped bearing means is connected effectively to the mass to be mounted, the bearing means in each case being designed as a bearing head provided with at least one magnet and with gas outflow nozzles.
It is also advantageous if the bearing heads of the first bearing element are pivotably mounted individually on a carrying structure connected effectively to the mass to be mounted. By virtue of this arrangement, any unevennesses in the metal plate and also slight exogenic disturbances exerting a tilting moment on the respective bearing heads can be compensated for, since the individual bearing heads in each case come to bear optimally against the sheet-like bearing element, without an increase in the distance between the two bearing surfaces and consequently a lifting-off of the bearing head from the second bearing element occurring at the same time.
It is particularly advantageous if the bearing heads of the first bearing element are arranged in a row, at least two bearing heads being provided, which in each case are articulated laterally moveably on one end of a balance-beam-like carrying beam, and the carrying beam being pivotably mounted indirectly or directly in the manner of a balance beam on a suspension structure for the mass to be mounted. This design makes it possible to have an ideally uniform distribution of the tensile force to the individual bearing heads and consequently a homogeneous and reliably effective distribution of tensile force over the entire bearing arrangement.
At the same time, it is particularly advantageous if the carrying structure has, in a first plane, an even number of first balance-beam-like carrying beams, at the respective ends of which two bearing heads adjacent to one another are pivotably mounted. It is further advantageous if the carrying structure has, in a second plane, a number of two balance-beam-like carrying beams, at the respective ends of which two first carrying beams adjacent to one another are pivotably mounted in the manner of a balance beam. It is desirable if the carrying structure has, preferably in one or more further planes, balance-beam-like carrying beams, at the respective ends of which two carrying beams, adjacent to one another, of the upper plane are pivotably mounted in the manner of a balance beam, and if the lowest plane has a single last carrying beam which is pivotably mounted in the manner of a balance beam on the suspension structure for the mass to be mounted. This design makes it possible to provide a multiplicity of bearing heads and, at the same time, ensure that each bearing head absorbs the same tensile force. Preferably, the magnets provided are permanent magnets. The advantage of this is that, in the event of a system failure, the mass suspended on the bearing arrangement does not fall down, but instead, due to the attraction force of the permanent magnet, acts on the second bearing element, so that the mass to be held does not fall down during a system failure.
It is also advantageous if at least one magnet is formed by a solenoid. It is thereby possible, for example, to provide a controllable braking device for a moving mass suspended on the bearing arrangement, and, by the solenoid being activated until the compressed gas cushion is overcome and there is physical contact with the second bearing arrangement, a braking action can be achieved by means of a bearing head provided with a solenoid. It is advantageous, in particular, if the attraction force of the solenoid and/or the repulsion force of the gas cushion are capable of being controlled or regulated. As a result, even a dynamic load can be controlled to a limited extent, and, by increasing the force of the solenoid and reducing the repulsion force of the gas cushion, a greater attraction of the bearing arrangement onto the second bearing element can be achieved.
A further object of the invention is to specify a bearing head for a generic mounting, into which bearing head a magnet is integrated.
This object is achieved in that a gas outflow structure is provided around the magnet in the bearing surface of the bearing head.
It is advantageous in this case if the gas outflow structure consists of a multiplicity of gas outflow nozzles arranged around the magnet, and, in particular, micronozzles may be provided, which ensure that a highly effective gas cushion is built up.
Alternatively, however, the gas outflow structure may also have at least one gas outflow nozzle which is fluidly connected to an air distributor structure arranged in a groove-like manner around the magnet.
In a particularly preferred embodiment of the bearing head, the housing is designed to be essentially axially symmetrical, preferably cylindrical, the bearing surface extending orthogonally, preferably all-round orthogonally, to the axis of symmetry of the bearing head, the magnet being arranged coaxially to the axis of symmetry of the bearing head, the inner flux lines of the magnet extending essentially parallel to the axis of symmetry, and the gas outflow nozzles being arranged around the magnet circularly on at least one ring which is likewise placed coaxially to the axis of symmetry. This special rotationally symmetrical design of the entire bearing head is distinguished in that, in the event of a movement, the bearing head does not have any directional priority, so that a movement of the bearing head in any translational direction is possible without obstructions and without preferences.
Alternatively to this, the bearing head may be designed in such a way that the bearing body has, in horizontal projection, a rectangular or trapezoidal form and that the magnet has, likewise in horizontal projection, a rectangular or trapezoidal form. An unequivocal directional preference of the bearing body is thereby afforded, and this may be advantageous if a predetermined direction of the movement of the bearing body is to be defined in a controlled manner, as may be advantageous, for example, in a transport system which uses the bearing arrangement according to the invention.
It is particularly advantageous if the gas outflow nozzles in the bearing surface are formed by microholes which are drilled by means of a high-energy beam and which are of conical form, their narrowest cross-section being located at the issue into the bearing surface. This form of the gas outflow nozzles, which is already known per se from DE 44 36 156 C1, has the advantage that the air consumption of the individual nozzles is extremely low and that a large number of nozzles for a high static carrying force can be introduced into the bearing body, without thereby causing the overall air consumption to rise into uneconomic ranges. In the bearing head according to the invention, this embodiment of the gas outflow nozzles, in conjunction with the magnet provided in the bearing head, provides extremely homogeneous attraction and repulsion of the cooperating bearing elements, so that these have a high reliable carrying capacity.
The bearing arrangement according to the invention, particularly when it is equipped with the bearing heads according to the invention, serves in a preferred use for the gravity-compensating suspension of a foldable solar panel arrangement for a satellite in a test apparatus for testing the deployment operation in a gravitational field so as to simulate weightlessness, at least one bearing arrangement being provided in order to suspend the solar panel arrangement so that it is freely moveable horizontally.
At the same time, it is particularly advantageous if a plurality of bearing arrangements are provided, a bearing arrangement of which in each case mounts one solar panel of the solar panel arrangement consisting of a plurality of solar panels, so as to be freely moveable horizontally in suspension and so as to be freely rotatable about the vertical axis running through the center of gravity of the respective solar panel. In particular, this embodiment makes it possible to ensure a moveability of the individual solar panels which is already frictionless in the suspension and, moreover, to prevent the occurrence of axial forces in the joints connecting the solar panels to one another, so that even in these joints no gravity-induced frictional forces take effect.
In principle, the bearing arrangement according to the invention and, in particular, the bearing heads according to the invention are also suitable for carrying out any other support of a suspended load, so that they can also be used, for example, for a conveying system which moves essentially without friction.
The invention is explained in more detail below by means of an example.